The present application is closely related to a commonly assigned copending U.S. patent application Ser. No. 09/047,215 U.S. Pat. No. 5,884,572 (corresponding to a Japanese Patent Application No. Hei-9-95094 entitled "Curved workpiece fabric holder device having rotary position adjusting mechanism for rotary frame for use in embroidery machine".
The present invention relates to a curved workpiece fabric holder device for holding a cup-shaped or cylindrical workpiece fabric such as a cap in order to perform embroidery stitching onto the workpiece while rotating the same about its axis.
A multiple-head type embroidery machine is provided for performing embroidery stitching to a plurality of workpieces simultaneously. The multiple-head type embroidery machine includes a plurality of embroidery machines, a plurality of cylinder beds, a fabric feed frame movable in a Y-direction(frontward/rearward direction) in parallel with an extending direction of the cylinder beds and an X-direction (lateral direction) perpendicular to the Y-direction, and an embroidery frames detachably installed onto the fabric feed frame for fixing workpieces at embroidery stitching positions. Further, a curved workpiece fabric holder device is provided for each embroidery machine so as to hold a curved workpiece fabric in order to perform embroidery stitching to each curved workpiece fabric while retaining the curved workpiece fabric in the holder device. A cup-shaped or a cylindrical workpiece can be referred to as the curved workpiece fabric. For example, a cap is a typical example of the cup-shaped workpiece.
As described in a Japanese Patent Application Kokai No. Hei-8-232158, a conventional curved workpiece fabric holder includes a base frame positioned adjacent the cylinder bed and movable in the Y-direction, a rotary frame rotatable about an axis extending in the Y-direction, a workpiece retainer detachably mounted on the rotary frame for fixing the curved workpiece at an embroidery stitching position, and a translation mechanism for translating a linear movement of the fabric feed frame in the X-direction into the rotating motion of the rotary frame. The base frame is linked to the fabric feed frame through a link mechanism, so that the base frame and the rotary frame can be driven in the Y-direction concurrently with the movement of the fabric feed frame in the Y-direction.
The translation mechanism includes a pair of right and left link plates releasably fixed to the fabric feed frame, a connecting rod movably connected to the base frame for connecting together the right and left link plates, and a wire partly wound over the rotary frame and having each end fixed to each link plate.
The wire looped around the rotary frame extends from a top end of the rotary frame toward each link plate fixed to a fabric feed frame, so that each end of the wire is fixed to each lower surface of the link plate by a fastener such as a screw.
If the pair of link plates are moved in the X-direction in accordance with the movement of the fabric feed frame, the rotary frame around which the wire is looped or wound is rotated about its axis, so that the curved workpiece and the retainer are also rotated. Thus, a desired stitching area can be brought into confrontation with a sewing needle.
In case a plurality of workpieces are to be stitched, a plurality of holder devices are mounted on the multiple head type embroidery machine. Here a distance between neighboring heads of the neighboring sewing machines is set in a predetermined distance, such as about 600 mm. In this connection, a pair of link plates for each holder device for fixing ends of each wire are set to the fabric feed frame in such a manner that the pair of link plates are not mechanically interfered with the neighboring link plates of different pairs. In each holder device, both fixed ends of the wire and the upper end of the rotary frame are aligned with each other in a horizontal direction. Because the rotary frame is not movable in the X-direction, the movement of the fabric feed frame in the X-direction causes rotation of the rotary frame through the translation mechanism.
Here, the embroidery stitching area is determinative by the rotation angle range of the rotary frame. That is, if the rotation angle range of the rotary frame is increased, the embroidery stitching area can be increased. In other words, the stitching area is determinative by the moving stroke of the fabric feed frame in the X-direction.
Further, the rotation angle range of the rotary frame is also dependent on a distance between the pair of link plates. If the pair of link plates are positioned far away from each other, a relatively long wire can be used so that rotation angle of the rotary frame can be increased. However, as described above, a distance between the pair of link plates is limited to avoid mechanical interference if a plurality of holder devices are installed onto the multiple head type embroidery machine. Therefore, it would be rather difficult to increase embroidery stitching area in the concurrent stitching in the multiple head type embroidery machine.